Wormhole, a popular interoperability protocol for bridging assets across different blockchains, has fallen victim to a hacking attack that resulted in the loss of approximately $320 million, or 120,000 ether.

This makes it the second largest DeFi hack to date, following a recent $80 million attack on Qubit Finance.

The exploit was confirmed in a tweet by the Wormhole team, who stated that they were working to add ETH over the next few hours to ensure wETH is backed 1:1, and that more details would follow shortly.

The protocol had earlier announced that the network was down for maintenance, with its website displaying a “Portal is Temporarily Unavailable” message.

Wormhole is a popular protocol that supports six different blockchains, including Solana, Ethereum, Terra, Binance Smart Chain, Avalanche, and Polygon.

The protocol allows users to bridge assets across blockchains, locking the transaction and minting a wrapped version such as wrapped ether (wETH) to its final chain.

At present, only wETH has been affected, with no other tokens compromised. While the hacker’s modus operandi is not yet known, the exploit took place over three different transactions at around 2:00 pm EST on Wednesday, according to Etherscan data.

Despite the loss, the Wormhole team remains hopeful of recovering the stolen funds. They have sent an on-chain message to the hacker, offering a reward of $10 million for exploit details and returning the wETH that was stolen.